Light-spot electrical measuring instrument

ABSTRACT

A switchboard light-spot electrical measuring instrument having an instrument movement with a permanent core magnet wherein an axial aperture is provided, an annular soft iron yoke surrounding the core magnet and having an aperture for passage of a light beam produced by an optical system, a moving coil being placed in the air gap formed between the core magnet and the annular yoke so that the core magnet is inside the moving coil, the moving coil being rotatably supported by means of a pair of taut bands passing through the axial aperture and arranged within the moving coil; the moving coil supporting a mirror near the aperture in the annular yoke between the core magnet and the annular yoke essentially within the height of the moving coil to reflect the light beam back through the aperture and onto a translucent screen with an adjacent scale plate.

United States Patent [72] Inventors Abram Markovich Damsky ulitsa Bratiev Vasilievykh, 7/4, kv. 6; Boris Abelevich Seliber, ulitsa Rentgena, 15/31, kv. 53, both of Leningrad, U.S.S.R. [2]] Appl. No. 6,029 [22] Filed Jan. 23, I970 [45] Patented July 20, 1971 I54] LIGHT-SPOT ELECTRICAL MEASURING INSTRUMENT 8 Claims, 10 Drawing Figs.

[52] US. Cl 324/97,

324/154 I [51] Int. Cl ..G0lr 13/38, v G01r 13/40 [50] Field of Search ..L 324/154, 151 A, 97

[56] References Cited v UNITED STATES PATENTS 602,527 4/1898 Sullivan 324/97 2,107,936 2/1938 Gardner 324/97 X 2,183,934 6/1937 Heiland 324/114 X 2,993,403 7/1961 Harries 324/97 X Primary Examiner-Alfred E. Smith Att0rneyWaters, Roditi, Schwartz & Nissen ABSTRACT: A switchboard light-spot electrical measuring instrument having an instrument movement with a permanent core magnet wherein an axial aperture'is provided, an annular soft iron yoke surrounding the core magnet and having an aperture for passage of a light beam produced by an optical system, a moving coil being placed in the air gap formed between the core magnet and the annular yoke so that the core magnet is inside the moving coil, the moving coil being rotatably supported by means of a pair of taut bands passing through the axial aperture and arranged within the moving coil; the moving coil supporting a mirror near the aperture in the annular yoke between the core magnet and the annular yoke essentially within the height of the moving coil to reflect the light beam back through the aperture and onto a translucent screen with an adjacent scale plate.

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r nn n the I mis s p s ompensated; cocrcivitypqm v v fThe'presentlinventionrelatestoedgewise lightvspotelectri cal measuring instruments of 'themovingcoiltype', chiefly intendedlfor switchboards and panel mountings.

edg'ewise light-spot electrical measuring instruments F Licrr'r-srofr-ititcrmchtg hansumucinmumcnr ,FlG.- I is ,ang-axialsection of moving-coil core-magnet measuring mechanism for' use in 'cdgeflight-spot electrical measuring instruments, according to the invention;

havin'g a moving coil energized by thecu'rrent to be measured and a permanent core magnet or a'sott iron core, i:e.'instru-' ments' of the DArsonvalor iron-core electrodynamometer 'rality affixed mirrors can be placed in the amar h ae or th that new w henna-rm rinstonce their height-tbwidth ratio' amounts' to about. 1:2. this factthe known instruments occupyan 1 unreasonably l'argesurface-.'of distribution switchboards-or 'c'ontrd desks, *the scsleslptoper occupying 30 per- Referring to the'drawings in detail the instrument provided I with the moving-coil pennanent-magnet measuring mechanism comprises a cylindrical permanent coremagnet l (FIGQ1)=andan-external annular soft-iron yoke 2,'both being fixed immovably. An annular air-gap is formed between the core magnet l and the soft-iron yoke 2, wherein a moving coil 3 rotates under' the action-of the torque developed due to the interaction between the currentto I be measured; flowing through-the moving-coil 3, and the magnetic field of the permanent magnet l in the air gap. A mirror 5' is fixedrigidly to themoving coil Sth'roug'h a holder 4 at the same height as the movingcoil.

: To the inertiamoment 6: the instrument movement comprising the movingcoil 3, the 'mirror5, and; the holderf4, themirror S'is vbrought- 'nearer to its rotation axis by. cutting out, symmetrically,thev parts of the cylindrical magnet l outside the active portions of the air gapand by making an tapermm in the annular yoke 2 for the passage ofthelight beam; v "The light beamis produced by an optical system comprising alight source 6, a condenser lens 7, a diaphragm 8, a fixed mirrorfl a'ndan objective lens 10; The light beam produced by the optical system "isvreflect'ed trom the mirror 5 and is'pro- It is the-principal object or thepresent inventionto provide an edgewise'ligh't electrical measuringinstrument with a considerablyreduced height-'to-width ratio.- For instance the ratio can be reduced to 1:5 and evento 1:6, aotha't the scale will occupy practically the'entire'face 'surtfscejotf the inslfir inent. .7 v 1 4 g This object i sachievad duet'o the fact thatfaccordingtothe' v at thea'anie height asthe having n This' makesit possible a decrefle substantially the oflhe measuring mechanism ;1-'l'= W W v sler h Mejia we?" "jcted onto the mat plane scale .11 jas'a light spot; 12 (Fl G. 2

position of which on the scale depends. on the rotation angle of the moving coil 3. The measuring-mechanismand the optical systemare placedinto an edgewise case 13 having the .height-to-width ratio amounting to 1:5 or even to l :6.

"Anyot the measuringmechanismsjdescribed below and usedjin edgewiseinstruments. 1 I

.' Asishown in FIGS. Sand 4 the moving-coil measuring made. in accordance with the present invention can also be f mechanism includes arectangularpennanent magnet 14 with I pole pieces l- S?andl6.'The measuring rriechanism further innearer mime rotation axis, provision-can be foranvaperture in the magnetic structure; The 'resultin'gde'c'reale in magit s 11 em w immanent "appareiitffromjaconsiderjation of the following-description of xempl ry wm mfnwt we aiawr i uieim mma m in whichr- FIG; schemati y a plan of light-spot electrical measuring instrument'coutprising amov- ,ing coil core-magnet measuring mechanism accordingft'o the present invention; I I

FIG. 1.; is a perspectivej view somewhat schematic of the r dss ikish i bm r w is instrument, a TMIQ Q iuvenliOn; V

FIGSHJ and schematically {plane and of a of the moving-coil permanent-magnet measuring mechanisrn'with a soft-iron core for uae in edgewiae light-spot electrical measuring instruments, according to the invention;

FIGS. 5 and represenfl'schematically; plan front views a f a at e' nin u s-c m ar- '65 net n'tea'siuring for use in edgewise light-Ispot elects m nr the enti Flos.'1 and ste mmchemm y; plan on side views of the iron-core electrodynamometer t'ype'rneasu rin use in edgewise' light-spot'elec' j iron-core electrodyn'smomete'r nts;'. sccording; to.the'inyeritionaand 4 I earn j lta achematscal" ly the unipolardouble-system l t spot electrical measuringinstrucludes a; movingcoil 17, inside which'ja soft-iron core 18 is placed. .The corej lfl' hasanlaperture wherein amirror l'9 is 9. located, mirror 19 =beingjfastened to the moving coil 17 at height level as that of-the moving coil 17 's -mum a' m send. me im a am measuring mechanism co'mprisjesia rectangular permanent mag eto apole piece zl; and a soft-iron yolteZZQThe yokellfh'as an arched portion 23 alongwhicha moving coil 24 rotates about the externa ge metrical axis. A mirror '26 is fixed'to' moving coil through a holder 25 at thesame meclianism of the ironktore eleetrodynamomete'r typeinclum ing a fixed field coil Z'I'which isplace'd on aprojection28 of a soft-iron yoke-29. The yoke 29 has'an arched portion 30 alongv which a moving coil 31 rotates about the external geometrical axis. A mirror 33'is fixed to the moving coil 3l through a holder 32 at tl esame heightasthe moving coil 31. FlG; 9 illhst'ratesfa "unipolar double-systenmeasuring mechanism ofthe iron-core electrodynamometer type; includin fixed fieldEcoils as and as placed on projections 36 and s1 otjsoft-iron yokes-SB and 39 respec'tively. The yokes 38 and 39 have arched portions 40 and 41', along which moving coils 42 mass travel. lhe'moving coils 42fand l 3 are connected by a holder ,to whicha mirror 4Sis'fastened, I

Reference]: now mad'e to FIG; '10 showing the measuring" mechanism of the presentinvention, comprising a moving coil 46 energised-by the current to be measured. The moving coil ,46 isrotatablymountedon taut-, suspension bands 47 and,

disposed,'essent ially,' alongth'e rotation axis of the moving coil.

46; lnsid ejthe moving coil 46 a cylindrical pennanentcore gitudinal aperture and. with radial" apertures normal to'each other and dilpole'din' two parallel planes, 's aid'apertu'res ac"- 7,5" commodating eylindricalpins 51.5; and wedges 53 $4.

magnet lg'is placedin-the central aperture of which a'cylindri- 1 cal bushing SO isinie'rted, said bushing being made of insulating material 'l'liebushing Sil'is provided witha through him.

The taut-suspension bands 47 and 48 are passed from opposite sides through the longitudinal aperture in bushing 50 and around pins 51, 2 against which the taut-suspension bands 47, 48 are pressed by the wedges 53, 54, then they are led out from the bushing 50 and welded to current leads 55, 56 fixed on the end face portions of the bushing 50. The bushing 50 is fixed in position by a slide member 57 and a blade spring 58.

The external portions of the taut-suspension bands 47, 48 are passed through the apertures in the moving coil 46 and around pins 59, 60, being then fixed to the periphery portions of flat disc springs 61, 62, said springs being turnablymounted inannular holders 63,64 fixed to the opposite sides of the moving coil 46. Y I g Holders :65, 66 fixed to the annular holders 63, 64 are used for fixing a mirror 67 to the moving coil 46. The moving coil 46, annular holders 63, 64, holders 65, 66 and mirror 67 constitute the instrument movement. The permanent magnet 49 together with the instrument movement is placed inside an annular soft-iron yoke 68 pressed in a frame unit 69 of plastic. The map et 49 is fixed to the frame unit 69 by a screw 70.-

ln the recesses made in the yoke 68 retainers 71 and 72 are placed, said retainerspreventing the instrument movement from undergoing displacements which may be caused by mechanical effects, and simultaneously the retainers serve as covers. The measuring mechanism is 'closed by a common cover 73 fixed by screws 74 (there is shown only one). For letting the light beam pass to the mirror 67 the yoke 68 is provided with an aperture 75, and the cover 73 has an aperture 75 closed by a glass plate 76.

Though the present invention is described in connection with a preferred embodiment thereof, it is evident that there may be made other modifications and variations without departing from the spirit and scope thereof, as will be clear to those skilled in the art.

We claim:

1. A switchboard light-spot electrical measuring instrument comprising an optical system for producing a light beam; a permanent core magnet having an axial aperture therein; an annular soft iron yoke surrounding said core magnet to form a gap therewith, said yoke being provided with an aperture for passage of the light beam therethrough; an instrument movebetween 'said core magnet and said annular yoke essentially within the height of the moving coil, the latter means fastening said mirror to said moving coil for common movement therewith; a scale plate having divisions thereon; and a translucent screen on which a light spot is projected by reflection from said mirror, said screen being disposed along said scale plate and in the same plane as said scale plate said mirror and said aperture in the annular yoke being of substantially the same height as said coil.

2. An instrument as claimed in claim 1, wherein said permanent core magnet is in the form of a cylindrical body, a part of which, opposite said aperture in the yoke, is removed.

3. An instrument as claimed in claim 1, wherein said core magnet is confined within the height of the moving coil.

4. An instrument as claimed in claim 1, comprising retainer means mounted in said yoke for said instrument movement and serving as a cover therefor. I

5. An instrument as claimed in claim 1 wherein said mounting means comprises a bushing mounted within said axial aperture in the core magnet, said ends of the taut bands being secured in said bushing.

6. An instrument as claimed in claim 5 wherein said tautbands have opposite ends which are fixed immediately outside the moving coil.

7. An instrument as claimed in claim 5 wherein said means mounting said mirror from said coil comprises flat annular holders fixed to said moving coil and having-apertures for passage of the taut-bands therethrough.

8. An instrument as claimed in claim 7, comprising flat members fixed in said yoke and rotatably supporting said annular holders, said taut-bands having opposite ends secured to said flat members. 

1. A switchboard light-spot electrical measuring instrument comprising an optical system for producing a light beam; a permanent core magnet having an axial aperture therein; an annular soft iron yoke surrounding said core magnet to form a gap therewith, said yoke being provided with an aperture for passage of the light beam therethrough; an instrument movement including a moving coil within said gap, said core magnet being inside said moving coil, mounting means extending within the moving coil and supporting said moving coil for rotation, said mounting means comprising a pair of taut-bands with ends secured within said core magnet and passing through said axial aperture and arranged within said moving coil, a mirror for reflecting the light beam, means extending externally of said coil and mounting said mirror adjacent said aperture in said annular yoke outside said core magnet and between said core magnet and said annular yoke essentially within the height of the moving coil, the latter means fastening said mirror to said moving coil for common movement therewith; a scale plate having divisions thereon; and a translucent screen on which a light spot is projected by reflection from said mirror, said screen being disposed along said scale plate and in the same plane as said scale plate said mirror and said aperture in the annular yoke being of substantially the same height as said coil.
 2. An instrument as claimed in claim 1, wherein said permanent core magnet is in the form of a cylindrical body, a part of which, opposite said aperture in the yoke, is removed.
 3. An instrument as claimed in claim 1, wherein said core magnet is confined within the height of the moving coil.
 4. An instrument as claimed in claim 1, comprising retainer means mounted in said yoke for said instrument movement and serving as a cover therefor.
 5. An instrument as claimed in claim 1 wherein said mounting means comprises a bushing mounted within said axial aperture in the core magnet, said ends of the taut bands being secured in said bushing.
 6. An instrument as claimed in claim 5 wherein said taut-bands have opposite ends which are fixed immediately outside the moving coil.
 7. An instrument as claimed in claim 5 wherein said means mounting said mirror from said coil comprises flat annular holders fixed to said moving coil and having apertures for passage of the taut-bands therethrough.
 8. An instrument as claimed in claim 7, comprising flat members fixed in said yoke and rotatably supporting said annular holders, said taut-bands having opposite ends secured to said flat members. 